EN 50104:2002

SLOVENSKI STANDARD
01-september-2002
1DGRPHãþD
SIST EN 50104:2000
(OHNWULþQHQDSUDYH]DRGNULYDQMHLQPHUMHQMHNLVLND=DKWHYH]DGHORYDQMHLQ
SUHVNXVQHPHWRGH
Electrical apparatus for the detection and measurement of oxygen - Performance
requirements and test methods
Elektrische Geräte für die Detektion und Messung von Sauerstoff - Anforderungen an
das Betriebsverhalten und Prüfverfahren
Appareils électriques de détection et de mesure de l'oxygène - Règles de performance et
méthodes d'essai
Ta slovenski standard je istoveten z: EN 50104:2002
ICS:
13.320 Alarmni in opozorilni sistemi Alarm and warning systems
29.260.20 (OHNWULþQLDSDUDWL]D Electrical apparatus for
HNVSOR]LYQDR]UDþMD explosive atmospheres
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN 50104
NORME EUROPÉENNE
EUROPÄISCHE NORM April 2002
ICS 19.080 Supersedes EN 50104:1998
English version
Electrical apparatus for the detection and measurement of oxygen -
Performance requirements and test methods
Appareils électriques de détection Elektrische Geräte für die Detektion
et de mesure de l'oxygène - und Messung von Sauerstoff -
Règles de performance Anforderungen an das Betriebsverhalten
et méthodes d'essai und Prüfverfahren
This European Standard was approved by CENELEC on 2002-02-01. CENELEC members are bound to
comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any
other language made by translation under the responsibility of a CENELEC member into its own
language and notified to the Central Secretariat has the same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Czech Republic,
Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands,
Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.
CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
Central Secretariat: rue de Stassart 35, B - 1050 Brussels
© 2002 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 50104:2002 E
Fore word
This third edition of the European Standard was prepared by SC 31-9, Electrical apparatus for the
detection and measurement of combustible gases to be used in industrial and commercial potentially
explosive atmospheres, of Technical Committee CENELEC TC 31, Electrical apparatus for explosive
atmospheres, on the basis of EN 50104:1998.
The text of the draft was submitted to the formal vote and was approved by CENELEC as EN 50104 on
2002-02-01.
This European Standard supersedes EN 50104:1998.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2003-02-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2005-02-01
Annexes designated „informative“ are given for information only.
In this standard, Annexes A and B are informative.
_________
– 3 – EN 50104:2002
Contents
Page
1 Scope .5
2 Normative references.5
3 Definitions.6
3.1 Gas properties.6
3.2 Types of instruments .6
3.3 Sensors .7
3.4 Supply of gas to instrument .8
3.5 Signals and alarms .8
3.6 Times .8
4 General requirements.9
4.1 Introduction.9
4.2 Construction.9
4.2.1 General.9
4.2.2 Indicating devices.9
4.2.3 Alarm or output functions . 10
4.2.4 Fault signal . 10
4.2.5 Adjustments . 10
4.2.6 Battery-powered apparatus. 10
4.2.7 Software-controlled apparatus . 10
5 Test methods. 10
5.1 Introduction. 10
5.2 General requirements for tests . 11
5.2.1 Samples and sequence of tests . 11
5.2.2 Preparation of apparatus before testing. 11
5.2.3 Mask for calibration and test. 12
5.3 Normal conditions for test . 12
5.3.1 General. 12
5.3.2 Test gas(es) . 12
5.3.3 Flow rate for test gases. 12
5.3.4 Voltage . 12
5.3.5 Ambient temperature . 12
5.3.6 Pressure . 13
5.3.7 Humidity . 13
5.3.8 Stabilisation time. 13
5.3.9 Orientation. 13
5.4 Test methods and performance requirements . 13
5.4.1 General. 13
5.4.2 Unpowered storage of the apparatus . 13
5.4.3 Calibration, adjustment and repeatability. 13
5.4.4 Drift (continuous duty apparatus only) . 14
5.4.5 Stability (spot-reading apparatus only) . 15
5.4.6 Alarm set point(s) . 15
5.4.7 Temperature . 16
5.4.8 Pressure . 16

5.4.9 Humidity . 17
5.4.10 Air velocity. 17
5.4.11 Flow rate. 17
5.4.12 Orientation. 18
5.4.13 Vibration . 18
5.4.14 Drop test. 19
5.4.15 Warm-up time (not applicable to spot-reading apparatus) . 19
5.4.16 Time of response. 20
5.4.17 Minimum time to operate (spot-reading apparatus). 20
5.4.18 Battery capacity. 20
5.4.19 Power supply variations . 21
5.4.20 Electromagnetic compatibility . 21
5.4.21 Addition of sampling probe. 22
5.4.22 Dust (for apparatus where the atmosphere is sampled by diffusion
only) . 22
5.4.23 Poisons and other gases . 22
5.4.24 Field verification kit . 22
6 Information for use. 23
6.1 Labelling and marking. 23
6.2 Instruction manual . 23
Annex A (informative) Sequence of tests . 26
Annex B (informative) Bibliography . 27

– 5 – EN 50104:2002
1 Scope
This European Standard specifies test methods and performance requirements for portable,
transportable and fixed electrical apparatus for the measurement of the oxygen concentration in gas
mixtures indicating up to 25 % (v/v).
In the case of inert gas purging (inertization), it applies also to apparatus with an oxygen measuring

function for explosion protection.
NOTE The most commonly used oxygen sensors in commercial equipment for industrial application are:
a) paramagnetic sensors;
b) electrochemical sensors (aqueous and solid electrolytes).
This European Standard is applicable to oxygen alarm apparatus intended to measure reliably the
oxygen concentration, to provide an indication, alarm or other output function, the purpose of which is to
give a warning of a potential hazard and, in some cases, to initiate automatic or manual protective
action(s), whenever the level exceeds or falls below a preselected alarm concentration.
It is applicable to apparatus, including integral sampling systems of aspirated apparatus, intended to be
used for commercial and industrial safety applications.
It does not apply to external sampling systems, or to apparatus of laboratory or scientific type, or to
medical equipment, or to apparatus used only for process control purposes.
2 Normative references
This European Standard incorporates by dated or undated references, provisions from other publications.
These normative references are cited at the appropriate place in the text and the publications are listed
hereafter. For dated references, subsequent amendments to or revisions of any of these publications
apply to this European Standard only when incorporated in it by amendment or revision. For undated
references the latest edition of the publication referred to applies.
EN 50270 1999 Electromagnetic compatibility - Electrical apparatus for the detection and
measurement of combustible gases, toxic gases or oxygen
EN 50271 2001 Electrical apparatus for the detection and measurement of combustible
gases, toxic gases or oxygen - Requirements and tests for apparatus using
software and/or digital technologies
EN 60068-2-6 1995 Environmental testing - Part 2: Tests - Test Fc: Vibration (sinusoidal)
(IEC 60068-2-6:1995 + corrigendum March 1995)

3 Definitions
For the purposes of this standard, the following definitions apply.
3.1 Gas properties
3.1.1
ambient air
normal atmosphere surrounding the apparatus
3.1.2
poisons (of sensors)
substances which lead to temporary or permanent loss of sensitivity of the sensors
3.1.3
reference air
air, under normal ambient conditions, with an oxygen concentration of (21 � 0,4) % (v/v)
3.1.4
standard test gas
test gas with a composition specified for each apparatus to be used for all tests unless otherwise stated
(see 5.3.2)
3.1.5
volume ratio (v/v)
ratio of the volume of a component gas to the volume of the gas mixture under specified conditions of
temperature and pressure
3.1.6
zero test gas
gas, such as nitrogen, which is free of oxygen, and interfering and contaminating substances
3.2 Types of instruments
3.2.1
alarm-only apparatus
apparatus having an alarm but not having a meter or other indicating device that would allow
measurement of the deviations permitted by the requirements of the appropriate chapters of this
European Standard
3.2.2
aspirated apparatus
apparatus that obtains the gas by drawing it to the gas sensor, for example, by means of a hand-
operated or electric pump
3.2.3
continuous-duty apparatus
apparatus that is powered for long periods of time, but may have either continuous or intermittent
sensing
3.2.4
cyclically operated apparatus
apparatus that senses several measuring points at time intervals
3.2.5
diffusion apparatus
apparatus in which the transfer of gas from the atmosphere to the gas sensor takes place by random
molecular movement, i.e. under conditions in which there is not aspirated flow

– 7 – EN 50104:2002
3.2.6
fixed apparatus
apparatus that is intended to have all parts permanently installed at a given location
3.2.7
oxygen alarm apparatus
portable, transportable or fixed apparatus to monitor the oxygen concentration in gas mixtures, which
measures autonomously and continuously or cyclically, warns and optionally switches, indicates,
registers and stores
3.2.8
portable apparatus
apparatus that has been designed to be carried readily from place to place and to be used while it is
being carried
A portable apparatus is battery powered and includes, but is not limited to
a) a hand-held apparatus, typically less than 1 kg, suitable for one-handed operation without
accessories (such as sampling probes, sample lines) fitted,
b) personal monitors, similar in size and mass to the hand-held apparatus, that are continuously
operating (but not necessarily continuously sensing) while they are attached to the user, and
c) another apparatus that can be operated by the user while it is carried either by hand, or by a
means of a shoulder strap or carrying harness, and which may or may not have a hand-directed
probe
3.2.9
spot-reading apparatus
apparatus intended to operate for periods of only a few minutes for irregular intervals
3.2.10
transportable apparatus
apparatus not intended to be portable, but which can be moved readily from one place to another
3.3 Sensors
3.3.1
integral sensor
sensor which is integral to the main body of the apparatus
3.3.2
measuring principle
type of physical or physico-chemical detection principle and the measurement procedure to determine
the measured value
3.3.3
remote sensor
sensor which is not integral to the main body of the apparatus
3.3.4
sensing element
part of the sensor which directly picks up the quantity to be measured and which is sensitive to that
quantity
3.3.5
sensor
assembly in which the sensing element is housed and which may also contain associated circuit
components
3.4 Supply of gas to instrument
3.4.1
sample line
pipeline by means of which the gas being sampled is conveyed to the sensor
3.4.2
sampling probe
separate sample line which is attached to the apparatus as required, that may or may not be supplied
with the apparatus. It is usually short (e.g. in the order of 1 m) and rigid (although it may be telescopic),
but it may be connected by a flexible tube to the apparatus
3.5 Signals and alarms
3.5.1
alarm set point
fixed or adjustable setting of the apparatus that is intended to pre-set the level of concentration at which
the apparatus will automatically initiate an indication, alarm or other output function
3.5.2
drift
variation in the apparatus indication with time, at any fixed gas concentration level under normal
conditions
3.5.3
fault signal
audible, visible or other type of output different from the alarm signal, permitting, directly or indirectly, a
warning or indication that the apparatus is not working satisfactorily
3.5.4
final indication
indication given by the apparatus after stabilisation
3.5.5
latching alarm
alarm that, once activated, requires deliberate action to be deactivated

3.5.6
measuring signal
signal of the sensor that is either not amplified or amplified with a constant factor
3.5.7
repeatability
closeness of agreement between the results of successive measurements of the same value of the same
quantity carried out by the same method, with the same measuring instruments, by the same observer,
in the same laboratory at quite short intervals of time in unchanged conditions
3.5.8
stabilisation
state when three successive readings of an apparatus, taken at 5 min intervals, indicates no changes
greater than � 1 % of the measuring range
3.6 Times
3.6.1
time of response tx (not applicable to spot-reading apparatus)
time interval, with the apparatus in a warmed-up condition, between the time when an instantaneous
variation in volume ratio is produced at the apparatus inlet and the time when the response reaches a
stated percentage (x) of the final indication

– 9 – EN 50104:2002
3.6.2
warm-up time (not applicable to spot-reading apparatus)
time interval, with the apparatus in a stated atmosphere, between the time when the apparatus is
switched on and the time when the indication reaches and remains within the stated tolerances
(see Figure 1)
4 General requirements
4.1 Introduction
Portable and transportable apparatus, as well as parts of fixed apparatus, that are used in potentially
explosive atmospheres shall conform to the appropriate regulations for explosion protection.
Apparatus intended for use in potentially explosive atmospheres shall not be used in oxygen enriched
atmospheres if an explosion hazard exists.
4.2 Construction
4.2.1 General
Gas detection apparatus or parts thereof (e.g. remote sensors) specifically intended for use in the
presence of corrosive vapours or gases, or which may produce corrosive by-products as a result of the
detection process (e.g. catalytic oxidation or other chemical process) shall be constructed of materials
known to be resistant to corrosion by such substances.
All apparatus shall be constructed to facilitate regular accuracy checks.
All materials and components used in the construction of the apparatus shall be used within the
manufacture’s ratings or limitations unless otherwise specified by appropriate safety standards.
4.2.2 Indicating devices
An indication shall be provided to show that the apparatus is energised.
NOTE The indication may be shown at the central unit.
When the apparatus is intended for the measurement of volume ratios of gases, the indicating or
recording device shall permit measurement of the permitted deviations specified in this standard.
For alarm-only apparatus or apparatus where the resolution of the read-out device is inadequate to
demonstrate compliance with this standard, the manufacturer shall identify suitable points for connecting
indicating or recording devices for the purpose of testing the compliance of the apparatus with this
standard.
Where a read-out device is inadequate, it shall be of sufficient quality as not to contradict the results
obtained by additional indicating or recording devices.
If the apparatus has more than one measuring range, the range selected shall be clearly identified.
If individual indicating lights are provided, they shall be coloured as follows:
a) alarms indicating the presence of gas at potentially dangerous levels shall be coloured RED;
b) equipment fault indicators shall be coloured YELLOW;
c) power supply indicators shall be coloured GREEN.
In addition to the colour requirements, the indicator lights shall be adequately labelled to show their
functions.
4.2.3 Alarm or output functions
If alarm devices, output contacts or alarm signal outputs are provided as part of fixed or continuous duty
portable apparatus and are intended to operate when a potentially hazardous gas concentration is
detected, they should be of a latching type requiring a deliberate manual action to reset. If a non-latching
type is used, this shall be indicated clearly and prominently in the instruction manual (see 6.2 k). Where
the outputs are connected to an integrated or auxiliary system, the means of latching and resetting may
be incorporated into these systems. If two or more set or alarm positions having the same purpose are
provided, the first alarm may be non-latching, depending on user preference. The integral or latching
device may reside in software.
4.2.4 Fault signal
Fixed and transportable apparatus shall provide a fault signal in the event of failure of power to the
apparatus. A short circuit or open circuit in connections to any sensor shall be indicated by a fault signal.
Automatically aspirated apparatus shall be provided
a) in the case of fixed and transportable apparatus: with an integral flow-indicating device that produces
a fault signal in the event of flow failure,
b) in the case of portable apparatus: with a means of verifying the air flow.
4.2.5 Adjustments
All adjustment devices shall be designed so as to discourage unauthorised or inadvertent interference
with the apparatus. Examples would include procedural devices, in the case of a keyboard instrument, or
mechanical devices such as a cover requiring the use of a tool.
Fixed explosion-protected apparatus housed in explosion-protected enclosures shall be designed so that,
if any facilities for adjustments are necessary for routine recalibration and for resetting or like functions,
these facilities shall be externally accessible. The means for making adjustments shall not degrade the
explosion protection of the apparatus.
The adjustments of the zero and signal amplification shall be so designed that adjustments of one will
not affect the other.
4.2.6 Battery-powered apparatus
Apparatus powered with integral batteries shall be provided with an indication of low battery condition,
and the nature and purpose of this indication shall be explained in the manual. All battery-powered
apparatus shall be so constructed that, when the apparatus is tested according to 5.4.18, it shall comply
with the requirements of this European Standard.
4.2.7 Software-controlled apparatus
In the design of software-controlled apparatus, the risks arising from faults in the programme shall be
taken into account.
Performance requirement: The apparatus shall fulfil the requirements of EN 50271.
5 Test methods
5.1 Introduction
The test methods and procedures described in 5.2 to 5.4 are intended as a basis for establishing whether
the apparatus conforms with the performance requirements given in this European Standard.

– 11 – EN 50104:2002
5.2 General requirements for tests
5.2.1 Samples and sequence of tests
For the purpose of type testing, the tests shall be carried out on one apparatus. Another apparatus may
be used for the tests according to 5.4.4, 5.4.22 and 5.4.23.
The apparatus shall be subjected to all of the tests applicable to that type of apparatus, as described in
5.4. The sequence of tests used during type testing shall be recorded. A recommended sequence is
given in Annex A.
Tests shall also be carried out, where applicable, to ensure that the apparatus satisfies the construction
requirements of 4.2. The requirements for these tests are generally self-evident, except that for short-
circuit requirements in 4.2.4, ballast resistors shall be substituted for each wire connecting the instrument
to any remote sensor. The values of these resistors shall be those declared, in the instruction manual, to
be the maximum lead resistances allowing satisfactory compliance with this European Standard. The
device used for the short circuit shall be of negligible resistance and shall be applied to convenient points
in the circuit, at the sensor ends of the ballast resistors.
For apparatus having more than one selectable range or scale, each range shall be tested. For the
second and subsequent ranges, the necessary amount of testing shall be agreed upon between the
manufacturer and the test laboratory.
5.2.2 Preparation of apparatus before testing
The apparatus shall be prepared and mounted as near to typical service as possible, in accordance with
the instruction manual, including all necessary interconnections, initial adjustments and initial
calibrations. Adjustments may be made, where appropriate, at the beginning of each test.
In particular, the following points shall be noted:
a) Apparatus having remote sensors
For the purpose of the tests in 5.4, where reference is made to exposure of the sensor to the test
conditions, the entire remote sensor (including any or all normally attached protective mechanical
parts) shall be exposed.
For apparatus having connection facilities for more than one remote sensor, only one remote sensor
needs to be subjected to the tests. The replacement of all but one sensor by „dummy“ impedances
yielding the worst case load conditions for the test in question shall be permitted. The worst case load
conditions shall be determined by the testing laboratory within the limits specified in the instruction
manual.
For apparatus having remote sensor(s), all tests shall be performed with resistances connected in the
detector circuit to simulate the maximum line resistance specified by the apparatus manufacturer,
except where minimum line resistance offers a more stringent test in the judgement of the test
laboratory.
b) Apparatus having integral sensors
The entire apparatus shall be exposed to the test conditions without removal of any normally attached
parts, including any sampling probe for tests 5.4.11, 5.4.15, 5.4.16 and 5.4.17.
c) For alarm-only apparatus, readings shall be taken using an external meter connected to test points
described in 4.2.2.
In all cases, optional parts shall be either attached or removed according to which condition will give the
most unfavourable result (at the discretion of the testing laboratory) for the test being conducted.

5.2.3 Mask for calibration and test
When a mask is used for calibration or for the injection of test gas into the sensor, the design and
operation of the mask used by the testing laboratory, in particular the pressure and velocity inside the
mask, shall not inadmissibly influence the response of the apparatus or the results obtained.
NOTE  It is recommended that the testing laboratory should consult with the manufacturer in determining the design of the calibration
mask. The manufacturer may provide with the apparatus a suitable calibration mask together with details of suggested pressure and rate.
5.3 Normal conditions for test
5.3.1 General
The test conditions specified in 5.3.2 to 5.3.9 shall be used for all tests, unless otherwise stated.
5.3.2 Test gas(es)
The volume concentration of oxygen in the standard test gas shall fall in the middle of the measuring
range as defined by the manufacturer, whereas the upper limit of the measuring range shall be not
greater than 25 % (v/v).
The tolerance on the nominal volume ratio of the standard test gas shall be within � 0,5 % (v/v) of
oxygen or � 10 % of the concentration of the standard test gas, whichever is less.
When the apparatus is intended for measuring oxygen deficiency or enrichment, all tests shall be made
with reference air and standard test gas.
When the apparatus is intended for measuring inertization, all tests shall be made with zero test gas and
standard test gas. For apparatus with a suppressed zero point, a test gas with the oxygen concentration
of the beginning of the measuring range shall be used instead of zero test gas.
When the apparatus is intended for more than one application, it shall be tested for each application.
The actual value of the concentration of the test gases shall be known within � 2 % relative.
NOTE The gas mixture may be prepared by any suitable method.
5.3.3 Flow rate for test gases
When the apparatus is exposed to the test gases, the flow rate of the gas shall be in accordance with the
manufacturer’s instructions.
NOTE For apparatus that samples by diffusion, either a calibration mask in accordance with 5.2.3 or a test chamber may be used.
5.3.4 Voltage
a) Mains-powered apparatus shall be operated within 2 % of the manufacturer’s recommended supply
voltage and frequency.
b) Battery-powered apparatus shall, for short term tests, be equipped with new or fully charged batteries
at the commencement of each series of tests. For long-term testing, it is permissible to energise the
unit from a stabilised power supply.
5.3.5 Ambient temperature
The ambient air and test gas shall be held at a constant temperature � 2 °C within the range of 15 °C to
25 °C, throughout the duration of each test.

– 13 – EN 50104:2002
5.3.6 Pressure
The tests shall be performed at pressures between 86 kPa and 108 kPa, with a maximum variation of
� 1 kPa throughout the duration of each test. For instruments susceptible to pressure variations, the
influence of pressure changes shall be taken into account, using the results of the pressure test (5.4.8).
5.3.7 Humidity
The relative humidity (r.h.) of the ambient air and the standard test gas shall be controlled to within
� 10 % r.h. over the range 30 % to 70 % r.h. throughout each test, except for tests 5.4.2, 5.4.7 and 5.4.9.
For short applications of test gases, the use of dry gases is permitted if agreed between the
manufacturer and the test laboratory. The properties of the sensor shall be considered, e.g. drying out.
NOTE Due allowance should be made for changes in oxygen concentration due to the presence of water vapour in the test gas
5.3.8 Stabilisation time
In each instance where the apparatus is subjected to a different test condition, the apparatus shall be
allowed to stabilise under these new conditions before measurements are taken.
5.3.9 Orientation
The apparatus shall be tested in the orientation recommended by the manufacturer.
5.4 Test methods and performance requirements
5.4.1 General
The following tests shall be performed in accordance with 5.3, unless otherwise stated. All tests shall be
performed. For all the tests, the apparatus (including the battery where fitted) shall be stabilised in
accordance with 5.3.8.
At the end of each test, indications shall be taken in both reference air or zero test gas and in the
standard test gas, unless otherwise stated. The values of the indications used for verification of
compliance with the performance requirements shall be the final indications (see 3.5.4) of both the
reference air or zero test gas and the standard test gas readings, unless otherwise stated.
5.4.2 Unpowered storage of the apparatus
All parts of the apparatus shall be exposed sequentially to the following conditions in reference air or
zero test gas only:
a) a temperature of - 20 °C � 3 °C for 24 h;
b) ambient temperature for at least 24 h;
c) a temperature of 50 °C � 2 °C for 24 h;
d) ambient temperature for at least 24 h.
Performance requirements: After being submitted to the conditions specified above, the apparatus shall
meet the requirements specified in clauses 5.4.3 to 5.4.24.
5.4.3 Calibration, adjustment and repeatability
5.4.3.1 Initial preparation of the apparatus
The apparatus shall be calibrated and adjustments shall be carried out, if needed, to obtain correct
indications in accordance with the manufacturer’s instruction manual.

For apparatus having more than one selectable range or scale, the necessary amount of testing shall be
agreed upon between the manufacturer and the testing laboratory.
5.4.3.2 Calibration curve
The apparatus shall be exposed to four test gases, two of which shall have an oxygen concentration at
the lower limit of the measuring range (e.g. zero test gas for apparatus intended for measuring
inertization) and an oxygen concentration near to the upper limit of the measuring range respectively.
The test gas volume ratios shall be evenly distributed over the measuring range. The gas with the lowest
oxygen concentration shall be applied first in the sequence, followed by the other test gases in order of
increasing oxygen concentration. The application of the first three gases shall be repeated in the reverse
order, i.e. in order of decreasing oxygen concentration, ending with the lowest concentration.
This operation shall be carried out three times consecutively, giving four measured values for the gas
with the lowest oxygen concentration, three at the highest oxygen concentration, and six at each of the
intermediate concentrations.
Performance requirements: After initial adjustment, each individual indication in the three sets of
indications (after correction using the manufacturer’s calibration curve, if necessary) obtained for each of
the four gas volume ratios shall not differ from these volume ratios by more than � 0,2 % (v/v) of oxygen
or � 2,5 % of the measuring range, whichever is the greater.
5.4.3.3 Repeatability
Expose the apparatus to zero test gas or reference air, and then to standard test gas and record the
measurement in each case. The duration of the application of the test gases shall be three times the time
of response t of the apparatus for concentration rise or concentration drop. Repeat this cycle nine more
times.
Performance requirement: The standard deviation of the values shown at the end of the gas application
shall be smaller than � 0,1 % (v/v) of oxygen or � 1 % of the measuring range, whichever is the greater.
5.4.4 Drift (continuous duty apparatus only)
NOTE For these tests, the apparatus may be powered by an external supply.
5.4.4.1 Fixed and transportable apparatus
The apparatus shall be operated continuously in reference air (apparatus intended for measuring oxygen
deficiency or enrichment) or in zero test gas (apparatus intended for measuring inertization) for a period
of one month. At the end of approximately every one week over the one-month period, the apparatus
shall be exposed to zero test gas or reference air, and standard test gas, depending upon the intended
use, until stabilised. Indications shall be taken prior to both the application and removal of each gas.
Performance requirement: The drift of measured values under zero test gas or reference air and under
standard test gas as determined by linear regression shall not exceed ± 2,5 % of the measuring range
per month or ± 0,2 % (v/v) oxygen per month, whichever is the greater.
5.4.4.2 Portable apparatus
The apparatus shall be operated continuously in reference air (apparatus intended for measuring oxygen
deficiency or enrichment) or in zero test gas (apparatus intended for measuring inertization) for a period
of 8 h per working day over a one-month period. At the end of approximately every one week over the
one-month period, the apparatus shall be exposed to zero test gas or reference air, and standard test
gas, depending upon the intended use, until stabilised. Indications shall be taken prior to both the
application and removal of each gas.

– 15 – EN 50104:2002
Performance requirement: The drift of measured values under zero test gas or reference air and under
standard test gas as determined by linear regression shall not exceed ± 2,5 % of the measuring range
per month or ± 0,2 % (v/v) oxygen per month, whichever is the greater.
5.4.5 Stability (spot-reading apparatus only)
The apparatus shall be exposed to standard test gas for 1 min followed by zero test gas or reference air,
depending upon the intended use, for 1 min. The operation shall be repeated 200 times. Indications shall
be taken prior to both the application and removal of each gas, after stabilisation at the end of the test.
NOTE For these tests, the apparatus may be powered by an external supply.
Performance requirement: The variation under zero test gas or reference air and under standard test gas

shall not be more than � 2,5 % of the measuring range or � 0,2 % (v/v) of oxygen, whichever is the
greater.
5.4.6 Alarm set point(s)
5.4.6.1 General
When the apparatus is provided with either
a) externally adjustable means of setting either one or more alarm set points, or
b) internally pre-set alarm point(s),
the activation of such alarms by gas at the appropriate set point values shall be verified by using test
gases as described in 5.4.6.2 and 5.4.6.3. In all cases, the test gas shall be applied until either activation
of the alarm(s) or twice the respective t , whichever is less.
For apparatus with several alarm set points, these tests shall be carried out for each alarm set point.
If a latching alarm is provided, the latching and the manual reset action shall be checked.
It shall not be possible to deactivate an alarm while the alarm condition is present.
The selected alarm set points shall not change when the measuring range is changed.
NOTE An additional acoustic alarm may be deactivated manually prior to other alarm conditions being reset.
5.4.6.2 Increasing oxygen concentration (apparatus intended for measuring oxygen deficiency
or enrichment)
For apparatus of type a), set the alarm set point at 10 % relative below the concentration of the reference

air. If the alarm set point cannot be set at this concentration the alarm shall be set as near as possible to
that concentration. In this case and for apparatus of type b), the test gas shall have a volume ratio of
10 % relative above the concentration of the alarm set point.
Expose the apparatus to standard test gas, and then to reference air or the specified test gas above.
Performance requirement: The alarm shall activate following application of the reference air or the
specified test gas.
5.4.6.3 Increasing oxygen concentration (apparatus intended for measuring inertization)
For apparatus of type a), set the alarm set point at 10 % relative below the concentration of the standard

test gas. If the alarm set point cannot be set at this concentration, the alarm shall be set as near as
possible to that concentration. In this case and for apparatus of type b), the test gas shall have a volume
ratio of 10 % relative above the concentration of the alarm set point.

Expose the apparatus to zero test gas, and then to standard test gas or the specified test gas above.
Performance requirement: The alarm shall activate following application of the standard test gas or the
specified test gas.
5.4.6.4 Decreasing oxygen concentration (apparatus intended for measuring oxygen deficiency
or enrichment)
For apparatus of type a), set the alarm set point at 10 % relative above the concentration of the standard
test gas. If the alarm set point cannot be set at this concentration, the alarm shall be set as near as
possible to that concentration. In this case and for apparatus of type b), the test gas shall have a volume
ratio of 10 % relative below the concentration of the alarm set point.
Expose the apparatus to reference air, and then to standard test gas or the specified test gas above.
Performance requirement: The alarm shall activate following application of the standard test gas or the
specified test gas.
5.4.6.5 Decreasing oxygen concentration (apparatus intended for measuring inertization)
For apparatus of type a), set the alarm set point at 10 % of the measuring range. If the alarm set point
cannot be set at this concentration, the alarm shall be set as near as possible to that concentration. In
this case and for apparatus of type b), the test gas shall have a volume ratio of 10 % relative below the
concentration of the alarm set point.
Expose the apparatus to standard test gas, and then to zero test gas or the specified test gas above.
Performance requirement: The alarm shall activate following application of the zero test gas or the
specified test gas.
5.4.7 Temperature
This test shall be performed in a temperature chamber having the capability of holding the sensor or
apparatus at the specified temperature within � 2 °C. When the apparatus (or the portion under test) has
reached the specified temperature, the sensor shall be exposed sequentially to zero test gas or reference
air, and then standard test gas, which shall be at the same temperature as the atmosphere in the test
chamber. The dew point of the test gases shall be below the lowest temperature of the test chamber and
kept constant during the test.
Tests shall be carried out at temperatures of - 10 °C, 20 °C and 40 °C.
Performance requirement: The variation of the indications from that at 20 °C in zero test gas or reference
air, and standard test gas shall not exceed � 5 % of the measuring range or � 0,5 % (v/v) of oxygen,
whichever is the greater.
5.4.8 Pressure
The effects of pressure variation shall be observed by placing the sensor or apparatus (including the
aspirator for aspirated apparatus) in a test chamber that permits the pressure of the test gases to be
varied. The pressure shall be maintained at the specified levels for 5 min, before a reading is accepted
or a test is made.
Tests shall be carried out at pressures of 80 kPa, 100 kPa and 120 kPa.
NOTE The pressure should be changed with a rate less than 10 kPa/h.
Readings shall be taken with zero test gas or reference air, and then standard test gas.

– 17 – EN 50104:2002
Performance requirement: The variation of the indications in zero test gas or reference air, and standard
test gas from that at 100 kPa shall not exceed � 2,5 % of the measuring range or � 0,2 % (v/v) of oxygen
or (for apparatus with sensors measuring the partial pressure of oxygen) � 22 % of the measured value
at 100 kPa, whichever is the greater.
5.4.9 Humidity
Zero test gas or reference air with the specified humidities shall be supplied separately to the sensor
using a temperature chamber or test mask. The procedure
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